%I #5 Nov 25 2018 12:30:08
%S 1,2,1,3,2,9,3,28,9,137,28,811,137,6884,811,75303,6884,1133287,75303,
%T 22573092,1133287,608722751,22573092,21933950111,608722751,
%U 1064082678978,21933950111,69200610896639,1064082678978,6047740350081131,69200610896639
%N Number of n X n binary matrices, symmetric about the diagonal and under 90-degree rotation, with no more than 1 one in any 2 X 2 subblock.
%K nonn
%O 0,2
%A _R. H. Hardin_, Aug 09 2008